This invention relates to bead insulation compositions, tire beads, methods of making tire beads, and also to methods of making tires.
Maintaining the shape and overall dimensions of the tire bead is critical for assembly and manufacture of high quality tires, however, conventional tire beads typically distort or deform during tire assembly and curing. Conventional bead insulation compositions typically have good bead wire adhesion and processability but do not maintain their shape and overall dimensions (i.e., geometry) in an uncured or green state. xe2x80x9cProcessabilityxe2x80x9d is a term understood by those skilled in the art, and is typically indicated by scorch resistance, viscosity and the ability of the rubber composition to be used in bead forming equipment known to those skilled in the art.
Numerous solutions have been adopted by those skilled in the art in an attempt to overcome the problem of distortion and deformation of the shape and overall dimensions of conventional tire beads during tire manufacturing, yet each has associated disadvantages. One solution has been to precure the green tire beads so as to provide a tire bead which will maintain its bead geometry during tire manufacturing. Conventional tire beads are typically precured in an autoclave at 285xc2x0 F. for 11 minutes. A disadvantage of precuring is that it raises manufacturing costs by adding an additional manufacturing step, raising energy costs and lowering tire bead manufacturing yields.
Two additional solutions, which also involve preprocessing steps, have been to wrap or staple tire beads. Wrapping the beads requires significant manpower and time, and, accordingly, significantly raises manufacturing costs. The disadvantages of stapling the bead are that special automatic equipment is required involving significant capital, increased operational complexity, lowered process yields, and, accordingly, also increased manufacturing times.
Tire manufacturing involves forcing two tire beads over the ends of a tire carcass. The tire carcass and conventional tire bead is then assembled with other tire components, such as the tread and side wall components, and then vulcanized. The tire bead must have dimensional integrity such that the tire bead can be placed over the tire carcass, and turned thereover, without distorting or deforming the tire bead.
U.S. Pat. No. 4,575,534 to Oshima et al., U.S. Pat. No. 4,540,744 to Oshima et al., U.S. Pat. No. 5,283,289 to Yamamoto et al., U.S. Pat. No. 5,098,941 to Tsuriya, and U.S. Pat. No. 3,715,266 to Winters et al. disclose conventional tire rubber compositions which contain uncrosslinked styrene butadiene rubber. In particular, the ""744 patent to Oshima discloses a tire rubber composition containing a butadiene polymer with a branched polymer through a tin-carbon bond and a styrene butadiene rubber. The ""289 patent to Yamamoto et al. discloses a fiber reinforced styrene butadiene containing rubber composition. The ""941 patent to Tsuriya discloses a phenolic resin reinforced bead filler composition having a low amount of hexamine which reduces the amount of deterioration of the tire carcass. The ""266 patent to Winters et al. discloses adding an adhesion component to conventional uncrosslinked styrene butadiene to improve the adhesion between the bead wire and the bead insulation composition. A disadvantage of these conventional tire rubber compositions is that they typically must be precured, cloth wrapped or stapled to maintain dimensional stability when used in making tire beads.
What is desired, therefore, is a bead insulation composition and tire bead that is dimensionally stable and that does not have to be preprocessed, but which provides sufficient bead wire adhesion and processability. Also desired is a method of manufacturing a tire using a dimensionally stable tire bead which exhibits sufficient bead wire adhesion and processability but which is not preprocessed, and a method of making a tire bead using a dimensionally stable bead insulation composition.
Accordingly, it is an object of the invention to provide a tire bead which does not have to be precured or cloth-wrapped or stapled before assembly into a tire.
Another object of the invention is to provide a tire bead insulation composition which has good adhesion to the tire bead wire, good processability, and which is dimensionally stable and does not require preprocessing.
Yet another object of the invention is to provide a method for manufacturing a tire bead utilizing a bead insulation composition having good bead wire adhesion and processability, yet which does not require preprocessing.
Still another object of the invention is to provide a method of manufacturing a tire using a tire bead that is not preprocessed yet which has good dimensional stability.
These and other objectives are achieved by the invention which provides a dimensionally stable ring for use as a tire bead, a tire bead, a tire bead rubber composition, a method of making a tire bead, and a method of making a tire. In another aspect, the objects are achieved by the invention which provides: a tape formed from a plurality of bead wires encapsulated and adhered by a dimensionally stable green rubber composition; a bead wire and a rubber composition containing a styrene butadiene rubber having crosslinked styrene butadiene and at least one other diene rubber; a styrene butadiene rubber having crosslinked styrene butadiene and at least one other diene rubber; adding a dimensionally stable green rubber composition to a plurality of bead wires to form a tape thereby encapsulating and adhering the bead wires; forming a dimensionally stable green tire bead comprising the step of adding a dimensionally stable green rubber composition to a plurality of bead wires to form a tape thereby encapsulating and adhering the bead wires, assembling the green tire bead with the tire carcass and other tire components and vulcanizing the tire assembly.
The invention and its particular features will become more apparent from the following detailed description considered with reference to the accompanying figures.